The present invention relates to reaction flavors, and more specifically to cooked flavors suitable for use in smoking compositions. The invention is also concerned with processes for preparing reaction flavors and incorporating them into smoking compositions, particularly those having a high content of tobacco stems, to produce a more acceptable and flavorful smoking product.
In general, tobacco stems and midribs represent an unsatisfactory portion of the cured tobacco leaf, from the standpoint of smoking, in the sense that they produce a stemmy taste on smoking and lack the desirable aroma and taste generally associated with tobacco lamina.
Stems are usually separated from the desirable leaf or lamina of tobacco. To throw away the stems and midribs is uneconomical and, for this reason, methods have been devised to modify and make them usable in smoking products. One of the methods which has been found to be relatively satisfactory, because of its simplicity and low cost, is to pass the stems between rollers in order to break up the bulky, rigid structure and to produce rolled stems, which are a flattened, loosened product which can be shredded and blended with shredded tobacco leaf.
It has been found, however, that the rolled stems still impart a certain amount of the harshness and off-taste which are imparted by tobacco stems to the smoke from cigarettes or other tobacco products into which they are introduced. Stems from burley tobacco are particularly undesirable in this respect. As a consequence, only a small portion of the stems from tobacco used in filler for cigarettes or cigars can be rolled and blended back into the filler.
We have now discovered a means by which rolled stems may be used to produce tobacco products having a more acceptable smoke. Stems from both bright and burley tobacco treated by our process may be used in greater proportion to produce a cigarette which yields comparatively bland smoke.
The present invention comprises contacting tobacco stems, either before, during or after passing the stems between rollers, with a solution of a reaction flavor product produced by reacting reducing sugars with a source of ammonia in the presence of trace amounts of amino acids.
The reaction of sugars with amino acids to produce desirable flavorants for smoking materials has generated increased interest. For example, U.S. Pat. No. 3,478,015 describes "browning reactions" in which an amino acid and a sugar having an active carbonyl are reacted in a lower alkyl polyhydric alcohol solvent in the absence of water at a temperature less than 90.degree. C. for about 5 to 15 hours. Generally the amino acid to solvent ratio is in the range of 1 to 3% by weight and the sugar to solvent ratio is in the range of 3 to 15% by weight. The reaction is carried out in such a manner that no free amino acid remains in the final product. The resultant reaction mixture is applied to tobacco to about 1% by weight of the tobacco.
U.S. Pat. No. 3,920,026 describes tobacco flavorants prepared by reacting valine with a carbonyl compound selected from sugars, dihydroxy acetone, or pyruvaldehyde. The molar ratio of amino acid to carbonyl compound can be from about 1:0.5-10, with a ratio of 1:4-5 being optimum. The reaction takes place in a solvent such as glycerol or propylene glycol and at a temperature between about 120.degree. and 200.degree. C., and preferably at about 150.degree. to 160.degree. C. for 0.5 to 5 hours depending on the type of sugar used. Flavanoid catalysts, such as quercetin or rutin or a hydroxyacid such as ascorbic acid, may be used. The reaction mixture may be applied directly onto tobacco or may be fractionated to separate the volatile and nonvolatile fractions, which are then used as tobacco flavorants.
U.S. Pat. No. 3,722,516 discloses the addition of dihydroxyacetone alone or in combination with amino acids to enhance the natural flavor characteristics of tobacco, and especially the caramel-like or burned sugarlike aroma thereof.
Japanese Pat. No. 9239/71 discloses certain tobacco "perfumes" such as 1-deoxy-1-L-prolino-D-fructose, which is a sugar-amino acid condensation product. This compound, as well as others, are prepared by reacting an amino acid with a sugar in an aqueous or alcohol solvent, and usually in the presence of an acid catalyst such as malonic acid. The desired compounds may be separated and purified by the use of ion-exchange resins and are thereafter applied to tobacco.
Japanese Pat. No. 3398/73 discloses certain other specific amino acid-sugars such as 1-deoxy-1-L-alanino-D-fructose that are synthesized from their respective components by the Amadori rearrangement, in the presence of malic acid as catalyst, by heating at 130.degree. C. for 15 minutes. The specific compounds are isolated and may be combined with cocoa to produce tobacco flavorants.
Two articles by Koehler (Journal of Agricultural Food Chemistry, Volume 17, Number 2, pages 393-396, 1969 and ibid., Volume 18, Number 5, pages 895-989, 1970) discuss pyrazine formation in sugar-amino acid model systems. The normal model system consists of asparagine and glucose reactants in a 1:1 molar ratio. Diethylene glycol solvent and a small amount of water are also used as solvents. The mixture is heated for 24 hours at 120.degree. C. The use of a base catalyst, such as sodium hydroxide or ammonium hydroxide, results in an increase in the production of volatile alkylated pyrazines. In some instances the addition of an aldehyde, such as acetaldehyde, appeared to increase pyrazine formation. Koehler's work was related to browning reactions known to occur in foods such as roasted peanuts, coffee, cocoa, and potato chips; and his primary object was to determine the chemical factors involved in volatile pyrazine formation during such reactions. Although volatile pyrazines were isolated and identified, there is no suggestion by Koehler that his reaction mixture would be suitable for use as a tobacco flavorant.
There is described in co-pending, commonly assigned U.S. application Ser. No. 029,244 filed Apr. 12, 1979 certain reaction flavors for smoking products wherein amino acids containing at least two nitrogens are reacted with reducing sugars and ammonium hydroxide in an essentially solvent-free system, and optionally in the presence of certain aldehydes. The ratio of reducing sugar to amino acid, based on weight, is in the range of about 2-8:1 and the ratio of sugar to ammonium hydroxide is approximately 3-10:1 based on the weight of the reactants. The reactants are heated for a period of time sufficient to reach a temperature in the range of about 90.degree. to 115.degree. C. and then cooled. The resultant flavorant, either diluted or undiluted, is applied to smoking compositions, and particularly reconstituted tobacco, at a level between about 0.001 to about 5% based on the weight of the composition.